DokuWiki Segmentation Fault On Radius Auth

http://serverfault.com –
I'm running x64 Ubuntu 12.04. I did a simple apt-get install dokuwiki to install DokuWiki. And I'm trying to follow the directions located here: http://www.dokuwiki.org/auth:radius to get Radius authentication working. Things seemed to install OK. Under Configuration Manager I selected Authentication backend to be "Radius" and filled in the Radius details at the bottom.
Now, however, whenever I try to log into the Wiki, my browser gives me the following error:
No data received
I checked /var/log/apache2/error.log and see this:
[Tue Jul 10 22:22:14 2012] [notice] child pid 5270 exit si
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